There has been in the past a continuing effort to develop a germicidal composition which is stable and cheap to manufacture.
The advantages of iodine condensed with a carrier, known as an iodophor and resulting in complex formation, over previously used iodine preparations such as Tincture of iodine and Lugol's solution are well documented.
The art is rich in attempts to efficiently produce an iodophor complex which is both cheap to prepare and stable over a period of time.
It was previously believed that such compositions needed a high PVP:I.sub.2 ratio for stability.
For example in U.S. Pat. No. 3,028,300 iodine and iodide are combined directly with polyvinylpyrrolidone, hereinafter known as PVP, in the dry state. U.S. Pat. No. 3,028,300 teaches that the PVP to iodine ratio must be at least 3:1 and the iodide to iodine ratio greater than 0.5. The disadvantage with this process is that the stability of the complex form decreases with decreasing proportions of PVP as shown in the tables illustrating the invention. No complex can be formed when the PVP to iodine is less than 3:1.
The process of U.S. Pat. No. 4,113,857 also uses for the iodine complex formation, oxidation of an iodine containing substance by an oxidising medium but with the following significant important difference to the present invention, namely the use of an excess of oxidising agent such as hydrogen peroxide or potassium iodate which leaves the final product free of iodide, claimed to be an essential and integral part of the invention. In contrast the present invention requires at least 10% of iodide calculated on the iodine of the complex.
U.S. Pat. No. 4,320,114 discloses a PVP-iodine complex wherein the complex is formed by combining, eg KI, PVP, and hydrogen peroxide. The pH is adjusted to between 2 and 7. The iodine is formed in situ by adding an oxidizing agent for partially converting the iodide ions into free iodine.
German Patent 27 18 385 discloses a process for forming a PVP-iodine complex by incomplete oxidation of iodide 4) and a ratio of PVP-iodine of approximately 5:1.
Spanish Patents 545 377 and 86-08317 disclose PVP-iodine complexes formed with a 10% excess of KIO.sub.3. Complete oxidation of the iodide would be expected. The ratio of PVP:iodine is 10:1.
United Kingdom Patent 2 084 875 discloses a composition in dry form, to be dissolved in water shortly before use. The iodophor is formed after dissolution in water. The ratios claimed are broad. The example discloses a 2:1 weight ratio for the PVP:KI, but no or little excess iodide would be expected as the iodide and the perborate are added in approximately equimolar amounts, based on the oxidizing strength of the perborate.
U.S. Pat. Nos. 3,898,326 and 4,017,407 provide iodine by direct addition.
U.S. Pat. No. 4,130,640 discloses a germicidal composition containing a sulfated fatty alcohol and/or a sulfosuccinates of a fatty alcohol in combination with PVP-iodine or iodine/iodide.
U.S. Pat. No. 4,402,937 requires that the ratio of iodine:iodide be about 2:1. The solution is stabilized with the addition of a reducing rather than an oxidizing agent which reduces iodine to iodide.
U.S. Pat. No. 4,526,751 discloses a weight ratio of about 2:1 for PVP:interhalogen solution and about 0.5:1 for iodide:iodine.
U.S. Pat. No. 4,038,476 discloses free-flowing granules of practically uniform composition and particle size consisting of PVP and iodide by combining with uniform thorough mixing a solution and/or colloidal suspension of a substance releasing iodide ions in a first solvent. The mixture as well as a solution and/or colloidal suspension and/or suspension of PVP in a second solvent or solvent mixture which possesses surface tension different from that of the first solvent or solvent mixture and in which PVP is at least partially soluble or wettable and in which the substance releasing iodide ions contained in the first solvent or solvent mixture is insoluble or only slightly soluble.
U.S. Pat. No. 4,125,602 is directed to the preparation of iodophor granules of practically uniform particle size consisting of PVP, iodine and a substance releasing iodide ions by combining with uniform thorough mixing a solution and/or colloidal suspension of elementary iodine and a substance releasing iodide ions in a first solvent or solvent mixture as well as a solution and/or colloidal solution and/or suspension of PVP in a second solvent or solvent mixture which has a surface tension different from that of the first solvent or solvent mixture and in which PVP is at least partially soluble or wettable and in which the substance is dissolved or suspended in the first solvent or solvent mixture are insoluble or only slightly soluble and separating and drying the granules formed.